1. Field of the Invention
The present invention relates to industrial control systems. More specifically, this invention relates to providing an operator with an interactive mobile wireless unit in order to communicate remotely with the industrial control system.
2. Description of Related Art
Manufacturing and process industries have become quite complex during the last few decades. Today, even a small manufacturing plant can easily contain several hundreds to several thousands of manufacturing and processing machines. These machines are usually connected to each other intricately to form sub-systems, which in turn, are connected to form larger systems, and so on, until together they form the entire plant. Since these individual machines are connected so intricately, a small variation in the output of one machine (or of an equipment) can easily result in malfunction of another machine or can even result in the final product being unacceptable. Hence, in all such industries today, there is a need to continuously monitor and control various chemical, mechanical and related processes.
In a typical industrial plant, which could, for instance, be a power plant, a refinery, a paper mill, or a petrochemical plant, a Distributed Control System (DCS) is used to monitor and control various processes. The Distributed Control System of the plant would usually have a centralised control room, and multiple controller and operator stations. The control room has a process controller and a process I/O subsystem. These are connected to the controller and operator stations through a communication bus. Since this communication bus is absolutely vital for the smooth operation of the plant, the bus is usually designed so that it has a high degree of fault tolerance and built-in redundancy. In addition to being connected to the controller and operator stations, the process 110 subsystem is also connected to various analog and digital field devices. Field devices are well known in the prior art related to control systems. The field devices include various types of analytical and monitoring equipment such as pressure sensors, temperature detectors, thermocouples, strain gauges, limit switches, on/off switches, flow transmitters, pressure transmitters, capacitance level switches, valve controllers and solenoids. The monitoring of various processes by the distributed control system usually involves collecting periodic data from these systems and controlling the parameters that govern these systems.
In rudimentary distributed control systems, any qualified user such as an operator, a technician or an engineer would periodically visit various machines and equipment and gather data from the associated measuring instruments. The same or a different operator would then collate and interpret this data, and, if required, prescribe a corrective action depending upon the results. Clearly such distributed control systems require a lot of human effort and are costly. Also, since it takes substantial time for the operator to gather, collate and interpret the data, such systems are not able to handle emergency situations. Hence, it is not surprising that most distributed control systems in manufacturing and processing industries have moved onto higher levels of automation and integration.
In contemporary automated distributed control systems, the monitoring and the control of various systems and sub-systems are done by a central process control system. In such systems, an operator would usually reside in the central process controlling area and would monitor and control different parameters of various machines and systems (from this central process controlling area). However, even in these automated systems, situations arise when an operator would have to physically visit a site and inspect a machine, a sub-system or an entire system, change set points or make other adjustments during times of ordinary production or process flow. Most production inspections are fairly routine and pre-scheduled. There can also arise inspections that are scheduled for regular or anticipated maintenance purposes. In addition, inspections may also be un-scheduled and some may even arise because of emergencies. One frequent example of such an un-scheduled inspection is when the operator suspects that certain monitoring equipment—such as a pressure sensor—is malfunctioning. In such a case, the operator is likely to physically visit the machine (or the system) and use his/her domain knowledge so as to identify and possibly rectify the problem. Indeed, when an operator visits the site, he/she would usually require real-time status information regarding the system (and/or other interconnected systems) so that the problem can be identified and rectified. Hence, proper co-ordination is required between the operator and the central process control system. There are several methods known in the prior art that provide status information of a system (or systems) to an operator when he/she visits a particular site; these are briefly discussed below.
In a simple implementation, each system is provided with a display terminal. The terminal collates the status information of the machine and equipment from the various sensors and measuring instruments. If required, the status information of this machine, or of the sub-system or the entire system, may be further collated by the central process control system and sent to this terminal. In some cases, the maintenance of a particular machine, sub-system or an entire system may require information to be gathered from connected systems. In such a case, this terminal may query other terminals (and/or the central process control system). After all the information has been retrieved and collated by the terminal, it is presented to the operator. The operator uses the information to identify the problem with the machine or the system. In some cases, the terminal may also provide the ability to control the machine or the entire system, by setting appropriate parameters, so that the operator can rectify the problem. This implementation suffers from two major drawbacks. The first drawback is that one terminal has to be provided for each machine to be monitored; hence, thousands of such terminals are required and this may render the entire solution economically infeasible (especially, if these terminals are being used only for infrequent inspections). The second major drawback is that in order to retrieve the information from other machines or from connected systems, the terminal may have to query the central process control system many times; consequently, a large number of such queries may result in over-loading of the central process control system.
An alternate solution provides a computer system and a terminal placed in each process section of the plant. This terminal would collate the information from various related systems in the process section, and provide a comprehensive report to the operator. This value added information would enable quicker inspection runs and faster identification of various faults in the systems. A modification of this solution is also proposed wherein these terminals may be provided with multiple profiles, i.e., different ways of presenting the status information. The status information is customised either locally on the terminal itself or centrally on the central process control system and then sent to the terminal. An important advantage of this modification is that operators with different expertise are presented different views of the same information. For example, the service technician may be provided a more detailed and exhaustive view of the status information compared to a more collated view for a process engineer. Clearly, since this information is suitably refined for the operator, this solution will improve the efficiency of the inspection process. Furthermore, since a computer system has been provided in each process section and since the terminal may collate and customise the status information, the load on the communication bus and on the central process control system is reduced. In today's automated industries, and unmanned process sections, it may not be feasible to provide each process section with a computer system and terminal, since these would not be utilized frequently.
A third solution known in prior art proposes equipping every technician with a mobile device. This mobile device communicates with a centralized computer system over a communication network. The communication network may be wired or wireless. In a wired implementation, the mobile device would be connected to the wired network, called a Local Area Network (LAN), at one of a finite number of LAN access points. In a wireless network, a wireless link (which may be formed using Radio Frequency (RF) waves, infrared waves, ultrasound waves, etc.) could be used to establish communication between the mobile device and the central process control system. The prior art proposes that the central process control system provides the mobile device with the status information of systems in the vicinity of the mobile device. In order to determine the systems in the vicinity of the mobile device, in both the wired and the wireless case, the physical location of the mobile device needs to be determined first. In the wired case, the location of the mobile device can be determined by its proximity to a particular wired access point, whereas, in the wireless case, several location-determining means that are already known in the prior art, may be used to locate the mobile device. (These means include placing a number of sources of electromagnetic waves in the field, and determining the location of the mobile device relative to these sources.) In this implementation, once the location of the mobile device has been determined, a means is required to identify the machine or the system for which the status information is required. In some implementations, the mobile device may itself point and identify the physical system for which the status information is required. Four patents given below disclose various kinds of mobile devices known in prior art.
WO Patent 9319414, which is titled “Portable exploitation and control system”, discloses a portable device for controlling one or more remote systems. This portable device communicates with the remote system over an unspecified wired or wireless communication link. It is envisaged that this portable device is provided with multiple application software for controlling multiple remote systems, wherein each remote system has a corresponding application software. The portable device is intended primarily for use with remote military devices, such as unmanned vehicles and electronic weapon systems. Accordingly, a rugged design of the device to facilitate use in the field is proposed. The invention does not elaborate on the nature of the communication link or the nature of information transmitted. Further, the invention is designed as a push system, wherein information or a control signal flows from the portable device to the remote system. In other words, it is the operator who can get information from the central process control system, and never vice versa.
WO Patent 9612993, which is titled “Apparatus for providing access to field devices in a distributed control system”, discloses an apparatus for providing wireless access to multiple field devices in a Distributed Control System. Field devices refer to devices that are typically found in various industries. These devices are generally remote from the central process control system. They include pumps, valves, pressure transmitters, temperature transmitters, flow transmitters and other such devices. All these devices are connected to a fieldbus control network. The fieldbus is a communication bus that forms the connection between the field devices and the central process control system. The invention contemplates that each field device is equipped with a wireless access port so that a wireless handheld device has access to the field device. In an alternative embodiment, the wireless access port can be located on a fieldbus module that provides access to a plurality of field devices. Thus a wireless handheld device can access these devices through this module.
U.S. Pat. No. 5,598,572, which is titled “Information terminal system getting information based on a location and a direction of a portable terminal device”, discloses a mobile device that points to and identifies the system to be inspected. The central process control system maintains a database of unique characteristics of each machine, sub-system and of each system. The invention suggests using the location, the physical appearance, the characteristic sound and/or the temperature profile of the system, to uniquely identify the system. Once the mobile device identifies a system, it conveys the observed characteristics to the central process control system, and the two together can distinguish the system based on its unique characteristics. Alternatively, the machine or the system may bear a unique identification code, such as a bar code, and the mobile device can be equipped with an identifying means, such as a bar code reader, to identify the system. Alternatively, the system may be equipped with a code-transmitting unit. This transmitting unit would then identify the system to a mobile device in its vicinity and the mobile device would identify the system appropriately. In either case, once the machine or the system has been uniquely identified, the unique identifier is used to query the central process control system to extract the status information of this machine, system and of other connected systems.
U.S. Pat. No. 6,167,464, which is titled “Mobile human/machine interface for use with industrial control systems for controlling the operation of process executed on spatially separate machines”, discloses a mobile device, called a Human-Machine Interface (HMI) that interacts with a wired LAN. The wired LAN connects various systems in an industrial plant and a central computer; this central process control system controls the processes occurring on these systems. Each local part of the system in the manufacturing or processing plant has status information and a control program. An operator uses the mobile device to query the state of a system. The mobile device communicates with the central process control system using a Radio Frequency (RF) link. The mobile device identifies the machine or the system by means as mentioned above and by other means that are well known in prior art. In one embodiment of this invention, the wired LAN is only used for process control and is not employed by the mobile device. In yet another embodiment of the same invention, the mobile device communicates with the local part of the system in the manufacturing or processing plant directly rather than with the central process control system. Further, the mobile device now broadcasts its identification over a short range RF link to a detector provided on each system. The detector uses the wired LAN to extract information and programs from the central process control system, and provides these to the mobile device. This invention also contemplates providing only the appropriate status information to various users operating on the mobile device.
The processes and systems in manufacturing and processing industries are becoming increasingly more complex. For these systems, the status information is often very complicated and still has to be interpreted in a short period of time. Thus, the need for a mobile device that can analyse and present this information in a suitable manner is imperative. The technologies are evolving at great pace and new and better functionalities are being added to these mobile devices. It would be beneficial if the mobile device may be able to interact with the central process control system and obtain the relevant information immediately. The mobile devices mentioned in the prior art extracted information primarily from a central repository.
The inventors envision that in order to quickly complete normal production, maintenance and inspection routines, the real-time information should be available at all levels and a more interactive and responsive mobile device is required. And, of course, such a mobile device has to be tailor-made for different users (with different profiles). Further, if there were a means of tracking these mobile devices, then a particular user, operator or engineer could be quickly located in an emergency. In addition to tracking the operator, information regarding the nature of the emergency could be quickly communicated. Further, the operator could then use the mobile device to check the status of other systems that may be affected (by such an emergency), and issue control instructions. The central process control system could then carry out these control instructions.
In addition to all the above-mentioned salient features in addition to normal production use (that are critical for handling emergencies and disruptions in real-time), there is a need for the mobile devices to be used by the operators in an interactive manner in order to effectively and efficiently schedule maintenance programs. Thus, enhancing the mobile computing device by incorporating a tracking means, will lead to significant productivity improvements.
The above-mentioned desirable characteristics of the mobile device can be implemented by the use of Radio Frequency (RF) devices. Short range wireless standards including HomeRF, 802.11, Bluetooth, and several others are being developed and deployed so that various mobile devices can be connected to wired LANs that already exist in buildings, plants, manufacturing companies, and warehouses. One standard known as Bluetooth protocol offers short-range communication between Bluetooth enabled devices by using wireless access points. Bluetooth technology uses radio waves at a frequency of 2.45 Giga Hertz and currently permits data transfer rates of up to 1 Megabit per second. The high data transfer rate enables Bluetooth devices to carry up to three simultaneous synchronous voice channels. Hence, these high data transfer rates permit increased interactivity. Further, Bluetooth uses spread-spectrum frequency hopping technology, wherein the frequency at which communication occurs, is switched periodically. This feature enables the mobile devices to remain networked even in noisy environments. Another important feature of Bluetooth enabled device is that it remains passively connected to the network, once a connection has been established. There is low energy consumption of the Bluetooth enabled device while it is not actively communicating with the network.